The present invention relates in general to safety and retraction mechanisms for presses. More specifically, the mechanism of this invention represents a unique safety interlock and retraction mechanism for clinching, crimping and punching presses, especially those presses as described in U.S. Pat. No. 5,937,694 issued to Mueller on Aug. 17, 1999. The aforesaid U.S. Pat. No. 5,937,694 issued to Mueller is hereby incorporated by reference. Many prior art presses as described in Mueller utilize one or more return springs to retract the ram from the work material and do not offer a safety interlock mechanism. When the aforesaid return spring(s) is used, the actuator must present a force upon the cams and cam rollers greater than the compressed spring force in order to actuate the ram toward the work material. Unfortunately, this results in less force upon the work material since the spring force must be overcome. Utilization of a return spring further limits the ram displacement due to the limitation on spring length within the fixed size frame and may also limit the ram retraction rate.
The present art represents an air cylinder retraction mechanism which eliminates the requirement for a return spring and further provides an interlock feature which prohibits full force actuation unless the desired work material having a predetermined thickness range is placed between a punch and die of the press. That is, the present art utilizes one or more pneumatic actuators having an internal return mechanism or spring and a pneumatic valve which allows only a nominal pneumatic actuator return force application to the ram unless the ram displacement is sufficient to indicate that a thinner or predetermined thickness of work material is between the punch and die and not a thicker material such as an operator's finger.
Accordingly, it is an object of the present invention to provide a press retraction mechanism apparatus and method of use which ensures safety and eliminates the need for a return spring to retract the ram from the work material.
Another object of the present invention is to provide a safety interlock apparatus and method of use which prohibits full force actuation of the press unless a predetermined thickness range of desired work material is placed between a punch and die of the press.
A further object of the present invention is to provide a safety interlock and retraction mechanism apparatus and method of use which provides an increased force upon the work material due to the absence of a counteracting return spring force.
A yet further object of the present invention is to provide a safety interlock and retraction mechanism apparatus and method of use which does not suffer the prior art limitations of ram displacement.